In a liquid crystal display device, a voltage is applied across two substrates to apply an electric field to a liquid crystal layer sandwiched between the two substrates, and thus liquid crystal molecules within the liquid crystal layer are deflected under the effect of the electric field so that the liquid crystal layer has a light transmittance corresponding to the electric field, thereby displaying pictures of different gray scales complying with the strength of the electric field. Additionally, to provide the liquid crystal molecules with a stable boundary condition in order to induce the liquid crystal molecules to be oriented in a certain direction, an alignment layer is formed on a surface of at least one substrate contacting with the liquid crystal layer. To enable the alignment layer to produce an alignment effect in a certain direction, a known method is to rub the alignment layer with a contact-type process, which, however, might scratch the alignment layer or cause pollution by particles. Thus, a contactless alignment process, for example a photo-alignment process, is proposed. In the photo-alignment process, linear polarized light irradiates the alignment layer to produce an alignment effect. The incident direction of the linear polarized light can determine the alignment direction of the alignment layer, and an included angle between the incident direction of the linear polarized light and the alignment layer may affect a pretilt angle of the liquid crystal molecules after the photo-alignment.
In the existing photo-alignment process, after both of the substrates are irradiated with light so that the liquid crystal molecules are oriented to an initial pretilt angle, both of the substrates processed to form a resultant liquid crystal cell. However, steps of such process are relatively complicated and cause a high cost.